linux-kernel - Re: [PATCH] PCI / ACPI / PM: Resume all bridges on suspend-to-RAM

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Message-ID: <20180816191515.GM2343@lahna.fi.intel.com>
Date:   Thu, 16 Aug 2018 22:15:15 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        teika kazura <teika@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PCI / ACPI / PM: Resume all bridges on suspend-to-RAM

On Thu, Aug 16, 2018 at 12:56:46PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 26112ddc254c (PCI / ACPI / PM: Resume bridges w/o drivers on
> suspend-to-RAM) attempted to fix a functional regression resulting
> from commit c62ec4610c40 (PM / core: Fix direct_complete handling
> for devices with no callbacks) by resuming PCI bridges without
> drivers (that is, "parallel PCI" ones) during system-wide suspend if
> the target system state is not ACPI S0 (working state).
> 
> That turns out insufficient, however, as it is reported that, at
> least in one case, the platform firmware gets confused if a PCIe
> root port is suspended before entering the ACPI S3 sleep state.
> 
> For this reason, drop the driver check from acpi_pci_need_resume()
> and resume all bridges (including PCIe ports with drivers) during
> system-wide suspend if the target system state is not ACPI S0.
> 
> [If the target system state is ACPI S0, it means suspend-to-idle
>  and the platform firmware is not going to be invoked to actually
>  suspend the system, so there is no need to resume the bridges in
>  that case.]
> 
> Fixes: c62ec4610c40 (PM / core: Fix direct_complete handling for devices with no callbacks)
> Reported-by: teika kazura <teika@....com>
> Tested-by: teika kazura <teika@....com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=200675
> Cc: 4.15+ <stable@...r.kernel.org> # 4.15+: 26112ddc254c (PCI / ACPI / PM: Resume bridges ...)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>